The invention relates to a method of electromagnetic coupling between a radar in the L band and a radionavigation equipment item and to an autoprotection and radionavigation device. In particular, the invention applies to the electromagnetic coupling between an aeronautical radionavigation equipment item called a DME (Distance Measurement Equipment) and a radar working for example on the L frequency band, on board one and the same carrier.
In order to protect civil or military aircraft in particular from hostile firing of ground/air missiles, these carriers bear autoprotection systems implementing doppler radars working in the L band as means of detection, suitable for detecting and classifying these threats. However, certain carriers, most particularly commercial aircraft, use a radionavigation equipment item called a DME (Distance Measurement Equipment) working in the same frequency band. The DME radionavigation equipment item may be jammed by the emissions of the L-band radar. According to the configurations of the antennas of these two equipment items, the jamming engendered by the operation of the radar may prevent the DME from functioning.
To sidestep this problem, a solution consists in adapting the DME radionavigation equipment item as well as the autoprotection system in such a way that each equipment item is able to synchronize itself with the emissions of the other, by emitting for example while the other equipment item is silent. In addition to the determination of a priority equipment item that is master over the other, the problem arises of modifying the DME radionavigation equipment item already installed on carriers so that it can receive a new exterior compatibility and synchronization signal. Such a modification requires that the DME radionavigation equipment item be recertified, giving rise to a significant extra cost.
Another solution resides in the optimization of the positioning and of the directivity of the antennas of the L-band radar with respect to the antennas of the DME radionavigation equipment item. By increasing the directivity of the antennas and by positioning them in such a way that the antennas of the radar are not in view of the antennas of the DME radionavigation equipment item, the risk of jamming is reduced. However, this solution increases the zones not covered by the L-band radar. Moreover, contrary to military aircraft, the integration of equipment items onto commercial aircraft may hardly be done outside of a few well-defined and limited zones.